Chapter 6. MPC8240 Memory Interface
6-29
SDRAM Interface Operation
6.2.11 SDRAM Registered DIMM Mode
The MPC8240 can be configured to support registered SDRAM DIMMs. To reduce
loading, registered DIMMs latch the SDRAM control signals internally before using them
to access the array. Enabling the MPC8240’s registered DIMM mode (MCCR4 bit 15,
REGDIMM = 1) compensates for this delay on the DIMMs control bus by delaying the
MPC8240’s data and parity buses for SDRAM writes by one additional clock cycle.
Enabling registered DIMM mode has no affect on the bus timing for SDRAM reads or
ROM/Flash transfers. However, the programmed read latency (RDLAT) time for SDRAM
reads must be incremented by one to compensate for the latch delay on the control signals
of the registered DIMM. Figure 6-15 shows the registered SDRAM DIMM single-beat
write timing.
Table 6-13. The MPC8240 SDRAM ECC Syndrome Encoding (Data Bits 32:63)
Syndrome
Bit
Data Bit
3
2
3
3
3
4
3
5
3
6
3
7
3
8
3
9
4
0
4
1
4
2
4
3
4
4
4
5
4
6
4
7
4
8
4
9
5
0
5
1
5
2
5
3
5
4
5
5
5
6
5
7
5
8
5
9
6
0
6
1
6
2
6
3
0
x
x
x
x
x
x
x
x
1
x
x
x
x x
x
x
x
2
x x x x x x x x x x x x x x x x
x
x
x
x
3
x
x
x
x
x
x
x
x x x x
4
x x x
x x x
x x x
x x x
x x x x
5
x x x x
x x x x x x x x x x x x
6
x x x x x x x x x x x x
x x x x x x x x
7
x x
x x
x x x x
x x x x x x x x
x x x
Содержание MPC8240
Страница 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Страница 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Страница 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Страница 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Страница 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Страница 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Страница 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Страница 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Страница 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Страница 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Страница 516: ...16 14 Watchpoint Trigger Applications ...
Страница 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Страница 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Страница 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...